Tracing control system

Abstract

A tracing control system for machining a workpiece through tracing by calculating speed commands of respective axes, using change amounts detected by a tracer head, and by moving a cutter relative to the workpiece through a control of the speed of the respective axes in accordance with the speed commands. First delay speed commands are obtained from the speed commands (Vx, Vz) at delay circuits (14a, 14c), respectively, and second delay speed commands are obtained at second delay circuits (14b, 14d), respectively, the differences between the first delay speed commands and the above second delay speed commands are calculated, and an X-axis main motor and a Z-axis main motor are driven in accordance with the first delay speed commands, and an X-axis sub-motor and a Z-axis sub-motor are driven in accordance with the calculated differences, thereby move the tracer head. As a result, the tracer head always precedes the cutter, and when the tracer head comes to a corner and the axis speed is reduced, the precedence amount of the tracer head is canceled out (relatively returned) by the amount corresponding to the speed reduction. This return amount can be made equal to the amount of over-run of the tracer head, and therefore, the amount of movement of the cutter is reduced by this over-run amount of the tracer head, to thereby prevent overshot machining.

We claim: 
     
       1. A tracing control system for machining a workpiece through tracing by calculating speed commands of respective axes, using change amounts detected by a tracer head, by moving a cutter relative to the workpiece through a control of the speed of the respective axes in accordance with the speed commands, and by moving the tracer head along the surface of a model, comprising: first delay means for obtaining first delay speed commands by delaying the speed commands by predetermined time constants;   second delay means for obtaining second delay speed commands by delaying the speed commands by time constants different from said predetermined time constants;   difference calculating means for calculating differences between the first delay speed commands and the second delay speed commands;   first axis moving means for moving a predetermined axis based on the first delay speed commands; and   second axis moving means for moving a specific axis in such that a movement of said specific axis is superimposed on a movement of the predetermined axis, and is parallel with the predetermined axis, based on said differences.   
     
     
       2. A tracing control system according to claim 1, wherein said stylus is attached to said specific axis. 
     
     
       3. A tracing control system according to claim 1, wherein the difference obtained by subtracting a leading time constant of said first delay means from a leading time constant of said second delay means is made equal to the difference obtained by subtracting a trailing time constant of said first delay means from a trailing time constant of said second delay means.